Chronic immune diseases can be highly debilitating, often requiring treatment. Two such chronic immune diseases are multiple sclerosis and chronic fatigue syndrome.
Multiple sclerosis (MS) is a neurological illness of unknown etiology associated with attacks of focal or multifocal neurological dysfunction indicating lesions within the central nervous system (CNS). In America and Northern Europe, MS is the most common neurological disease, with prevalence rates estimated between 50–100 per 100,000 population. The onset of disease is most common in early adulthood. Recurrent attacks can occur over many years, with approximately 30 percent of the patients progressing to a severe form of the disease which can be fatal.
MS is pleomorphic in its presentation. The clinical manifestations are determined in part by the location of the foci of demyelination within the CNS. Classical features of the disease include impaired vision, nystagmus, dysarthria, ataxia and intention tremor, and weakness/paralysis of one or more limbs. The demyelination is likely due to an autoimmune, inflammatory response that results in the destruction of the myelin sheath covering the axon of the peripheral nerves in the CFS.
The most common form of the disease is episodic. Symptoms develop with subsequent recovery, followed by another attack. In approximately 50 percent of all patients with MS, attacks become more frequent, usually with a worsening of symptomatology. In 30 percent, the disease develops into what is referred to as “progressive/relapsing,” the most severe form of the disease. In this state remissions are rare and patients frequently become wheelchair bound.
The diagnosis of MS remains problematic, and frequently the disease is not diagnosed until the patient has experiences two or more “attacks.” To aid the clinician, the only laboratory test available is testing the cerebrospinal fluid for oligoclonal bands, present in approximately 90 percent of all patients. Examination of the brain for demyelinating plaques, using magnetic resonance imaging (MRI) is useful but expensive and is not warranted except in a small group of patients in which all other clinical and laboratory tests are negative.
There is no diagnostic laboratory test to determine if a patient is having an “attack,” to monitor the progress of the “attack,” to determine if the patient is progressing to a more active form of the disease (i.e., progressive/relapsing), nor is any laboratory test available as a prognostic indicator and/or to monitor therapy if administered.
Chronic Fatigue Syndrome (CFS) is an illness of unknown etiology. CFS is often associated with sudden onset, flu-like symptoms, debilitating fatigue, low-grade fever, myalgia and neurocognitive dysfuntion. CFS patients typically display reduced Karnofsky Performance (KPS) scores. The KPS measures an individual's ability to function and carry on normal activities. KPS scores range from zero (0) for a completely non-functional or dead patient to one hundred (100) for a completely normal function.
Diagnosis of CFS remains one of exclusion. An accumulating body of evidence suggests that CFS is associated with dysregulation of both humoral and cellular immunity, including mitogen response, reactivation of viruses, abnormal cytokine production, diminished natural killer cell function and changes in intermediary metabolites.
It has been suggested that the clinical and immunological abnormalities observed in MS and CFS might be caused by defects in the interferon-inducible pathways i.e., the 2′-5′-oligoadenylate (2-5A) synthetase/RNase L and p68 kinase (PKR) antiviral defense pathways (Suhadolnik et al., Clin. Infect. Dis. 18:S96–S104, 1994; Suhadolnik et al., In Vivo 8:599–604, 1994). The 2-5A synthetase/RNase L pathway is part of the antiviral defense mechanism in mammalian cells (Lengyel, Ann. Rev. Biochem. 51:251–282, 1982; Sen et al., Adv. Virus Res. 42:57–102, 1993).
When activated by dsRNA, 2-5A synthetase converts ATP to 2′-5′-linked oligoadenylates with 5′ terminal phosphates. Biologically active 2-5A binds to and activates a latent endoribonuclease, RNase L, which in turn hydrolyzes single-stranded cellular and viral RNA, primarily after UpNp sequences, thereby inhibiting protein synthesis. In addition, circulating white blood cells from patients with CFS have been demonstrated to contain abnormal, low molecular weight forms of RNase L (Suhadolnik et al., J. Interferon & Cytokine Res. 17:377–385, 1997; De Meirleir et al., Am. J. Med. 108:99–105, 2000).
The 2-5A synthetase/RNase L antiviral pathway has also been demonstrated to play an important role in the regulation of cell growth and differentiation, specifically in the regulation of apoptosis as an additional host defense mechanism against viral infection and replication (Castelli et al., J. Exp. Med. 186:967–972, 1997; Diaz-Guerra et al., Virology 236:354–363, 1997). Apoptosis, defined as programmed cell death, plays an important role in many physiological and pathological conditions including embryo and organ development, immune responses, and tumor development and growth. Apoptosis is characterized by many biological and morphological changes at the cellular level including activation of calpain, caspases, DNA fragmentation, membrane blebbing and the formation of apoptotic bodies.
Another important protein that regulates the induction of apoptosis is p53 (Atencio et al., Cell Growth & Differentiation 11:247–253, 2000). The p53 protein is normally activated in response to genetic damage within the cell and its activation is accompanied by self-stabilization, allowing it to accumulate to high levels and cause cell cycle arrest and induce apoptosis (Kubbutat, M. et al., Mol. Cell. Biol. 17:460–468, 1997).
In addition, the p53 protein has a critical role in protecting the cell from malignant development; mutations in the p53 gene (and protein) are the most frequently detected genetic event in cancer (Hollstein et al., Nucleic Acids Res. 22:3551–3555, 1994). Mutations in p53 may occur at the genetic level (i.e. DNA sequence alterations that change the amino acid structure of the protein), or its function may be altered by alterations in the numerous proteins with which p53 interacts. p53 may also be altered by the action of certain proteases, resulting in cleavage, preventing the formation of active tetramers of the protein (Vogelstein et al., Nature 408:307–310, 2000).
If p53 is cleaved and/or otherwise disabled in the cells of the immune system, these cells would be being blocked from entering the apoptotic pathway if infected with a virus or other microorganism. In addition, persistent inactivation of the p53 protein may lead to increased incidence of cancer (Levine et al., J. Chronic Fatigue Syndrome 7:29–38, 2000). Activation of the 2-5A synthetase/RNase L antiviral pathway has been demonstrated to induce apoptosis, while induction of the same pathway in cells expressing mutant forms of p53 was demonstrated to suppress the apoptotic pathway.
The inactivation of p53, RNase L, and other proteins within the cells of the immune system most certainly leads to a dysfunctional immune system, unable to respond to challenge by microorganisms and/or the presence of pre-malignant cells. Indeed the immune system itself may be in a pre-malignant state.
To accurately diagnose and quantify the extent of chronic immune disease present in a patient, new markers of disease are required. In addition, methods are needed to treat chronic immune disease conditions. The present invention satisfies these and other needs in the art.
Relevant Literature
U.S. Patents of interest include: U.S. Pat. Nos. 5,766,859; 5,776,690; 5,830,668; 5,853,996, 5,955,263, 5,985,565, 6,017,524, 6,090,566, 6,110,671, 6,140,058, 6,153,391, 6,153,591, 6,169,073, and 6,184,210. Also of interest is WO 91/00097. Other references of interest include: Kastan et al., Cancer Res. 51:6304–6311, 1991; Kuerbitz et al., Proc. Natl. Acad. Sci. 89:7491–7495, 1992; Lowe et al., Nature 362:847–849, 1993; Clark et al., Nature 362: 849–852, 1993; Lowe et al., Cell 74:957–967, 1994; Pariat, et al. Mol. Cell. Biol. 17:2806–2815, 1997; Komaroff, Am. J. Med. 108:69–71, 2000.